Consider translation of the following mRNA sequence: 5′-...AUG...

Question

Consider translation of the following mRNA sequence: 5′-...AUGCAGAUCCAUGCCUAUUGA...-3′ What events occur to permit the next tRNA to interact with mRNA?

Accepted Answer

Hi, everyone. Welcome back. Here's our next question. Which of the following statements about translation is incorrect. So I'm going to read through our answer choices and we'll evaluate them as we go along remembering that we're looking for an untrue or incorrect statement about the process of translation. So, Cho says during the initiation, the ribosome binds M R N A at the A U G start codon and recruits an initiator T R N A carrying methionine. Well, this is a true statement. The ribosome does bind at the A U G start codon and that is a coon for the amino acid methionine. So unlike the star stop codons, which are antisense codons, they do not code for an amino acid. The start codon actually does code for an amino acid meth. So choice A is correct and therefore we will cross that out because it can't be the incorrect answer we're looking for. Then we have choice B which says during elongation, the ribosome moves along our M R N A in a five prime to three prime direction. And the next T R N A with complimentary anti codon enters the A site. Well, this is also a true statement. So an elongation as it sounds, we have new amino acids being added along added on to our growing polypeptide chain elongating it. The ribosome is indeed moving along in a five prime to three prime direction. And as it's being elongated, that happens as T R N A s with complementary anti codons enter the a site of the ribosome. Easy to remember because you think a, you think amino acid, but since this is a correct statement, we can go ahead and rule out choice B as our answer, then choi says during peptide bond formation, the ribosome catalyzes peptide bonds between amino acids at the A site and the growing polypeptide. Well, here's another true statement. The ribosome is what catalyzes that peptide bond formation and that happens between the amino acid that has been brought into the A site by the T R N A and the polypeptide chain that's being held at the P site. I think P for polypeptide in the ribosome. So since this is true, we'll go ahead and cross out choice C as well. So now we're just down to our last answer. Choice. Choice D which says during translocation, the ribosome moves along M R N A in a three prime to five prime direction, shifting the T R N A at the P site to the A site and the T R N A at the P site exits. Well, here we go unsurprisingly we're down to the last answer. This answer is incorrect or we'll put false by this and it's got several things wrong with it. So, first of all, during translocation, that process of the whole polypeptide change, shifting down or the ribosome shifting along to the next spot, the ribosome moves in a five prime to three prime direction, not a three prime to five prime direction. So that's our first problem. And then it says it shifts the T R N A at the P site to the A site. Well, this is not correct. The T R N A at the P site gets shifted to the site. You have our three sites. The amino acid comes in at the A site to start with, then gets shifted to the P site once the polypeptide bond or once the peptide bond is formed between that amino acid and the chain, and then finally gets shifted over to the site where it exits the ribosome. So that leads us straight to the final part of our statement that the T R N A at the P site exits. Well, again, we have a clue right in the letter, it's the T R N A at the E site that exits the ribosome E for exit. So for our incorrect statement, we have choice d during translocation, the ribosome moves along M R N A in a three prime to five prime direction. Shifting the T R N A at the P site to the A site and the T R N A at the P site exits. See you in the next video.

Consider translation of the following mRNA sequence: 5′-...AUGCAGAUCCAUGCCUAUUGA...-3′ What events occur to permit the next tRNA to interact with mRNA?

Key Concepts

Translation Process

tRNA Structure and Function

Ribosome Function

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